Thermal and chemical induced expansion of La0.3Sr0.7(Fe,Ga)O3-delta ceramics

authors	Kharton, VV; Yaremchenko, AA; Patrakeev, MV; Naumovich, EN; Marques, FMB
nationality	International
journal	JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords	ionic conductivity; (La, Sr) (Fe, Ga)O-3; membranes; perovskites; thermal expansion
keywords	PEROVSKITE-TYPE OXIDES; OXYGEN-ION CONDUCTORS; FORMER SOVIET-UNION; INDUCED STRESSES; TRANSPORT; CONDUCTIVITY; MEMBRANE; ELECTROCHEMISTRY; SEPARATION; DIFFUSION
abstract	The linear thermal expansion coefficients (TECs) of perovskite-type La0.3Sr0.7Fe1-xGaxO3-delta (x=0-0.4), determined by dilatometric and high-temperature X-ray diffraction techniques, are in the range (19-41)x 10(-6) K-1 at 770-1170 K, decreasing when the oxygen partial pressure or gallium concentration increases. At oxygen pressures from 10(-4) to 1 atm, the isothermal chemically induced expansion of La0.3Sr0.7Fe(Ga)O3-delta ceramics is a linear function of the oxygen nonstoichiometry. The magnitude of changes in 8 and, thus, chemical expansion both are reduced by gallium doping. The ratio between isothermal chemical strain and nonstoichiometry variations, (epsilonC/Deltadelta), follows an Arrhenius-type dependence on temperature and varies in the range (1.7-5.9)x 10(-2). The drastic increase in the thermal expansion at temperatures above 700 K, typical for ferrite-based ceramics, was shown to be mainly apparent, resulting from the chemically-induced expansion of the lattice due to oxygen losses. The TEC values, corrected for the chemical strain on heating, are close to the TECs at low temperatures and increase with gallium content. The observed correlations between the thermal and chemical expansion and ionic conductivity of La0.3Sr0.7Fe1-xGaxO3-delta are discussed in terms of their relationships with the oxygen deficiency and cation composition. (C) 2002 Elsevier Science Ltd. All rights reserved.
publisher	ELSEVIER SCI LTD
issn	0955-2219
year published	2003
volume	23
issue	9
beginning page	1417
ending page	1426
digital object identifier (doi)	10.1016/S0955-2219(02)00308-4
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000183376600009